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Scientific name: Wilsonia pusilla
The male Wilson’s Warbler is quickly recognized by his yellow plumage and round, black cap. An extensive breeding range from Alaska all the way to to eastern Canada, and migration to Mexico and areas south for the winter, makes it a common migrant across all of the U.S. Wilson’s Warblers migrate at night.
A single brood is most common in Wilson’s Warblers, but some pairs do attempt to raise a second brood. Nests are never reused, either in the same season or in a subsequent season. Nest parasitism by the Brown-headed Cowbird is rather rare.
2nd image © Greg Lavaty.
Description of the Wilson’s Warbler
The Wilson’s Warbler has greenish upperparts and wings, and yellowish underparts. Its black eyes stand out on its yellow face.
Males have a black cap.
Females have a mostly greenish cap.
Photograph © Greg Lavaty.
Seasonal change in appearance
Fall birds are slightly plainer, with males having more greenish in the cap.
Fall immatures are similar to but somewhat plainer than fall adults.
Wilson’s Warblers inhabit willow and alder thickets, streamsides, and low shrubs undergrowth.
Wilson’s Warblers eat insects.
Wilson’s Warblers forage actively in low shrubs, and sometimes flycatching.
Wilson’s Warblers breed from Alaska across central and eastern Canada and in parts of the northwestern U.S. During migration, they can be seen across most of the U.S. They winter in Mexico and Central America. The population may be declining.
Bent Life History
Visit the Bent Life History for extensive additional information on the Wilson’s Warbler.
Wilson’s Warblers are much more common in the western U.S. than in the east.
Wilson’s Warblers breed as far north as the timberline.
During the winter, individual Wilson’s Warblers may defend a territory, “float” between territories, or join a mixed-species foraging flock
The song is a quick series of chattered, whistled notes. A sharp “jip” call is also given.
- Hooded Warbler
Females of the two species somewhat similar. Hooded Warblers are larger and have white outer tail feathers.
- Yellow Warbler
Female Yellow Warbler similar to female Wilsons, has yellower back.
The Wilson’s Warbler’s nest is a cup of leaves, grasses, and mosses and is lined with finer materials. It is placed on the ground in mossy areas or at the base of a shrub.
Number: Usually lay 4-6 eggs.
Color: Whitish with darker markings.
Incubation and fledging:
The young hatch at about 10-13 days and fledge at about 8-13 days, though remaining dependent on the adults for some time.
Bent Life History of the Wilson’s Warbler
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the Wilson’s Warbler – the common name and sub-species reflect the nomenclature in use at the time the description was written.WILSON’S PILEOLATED WARBLER
WILSONIA PUSILLA PUSILLA (Wilson)CONTRIBUTED BY WINSOR MARRETT TYLER
Wilson (1832) and Audubon (1941) knew little about Wilson’s pileolated warbler. Wilson apparently saw only a few migrating birds in New Jersey and Delaware, and Audubon, although he “found the birds abundant in Newfoundland,” evidently did not discover its nest, as he describes it “amongst the thick foliage of dwarf firs, not more than from three to five feet from the ground.”
Spring: Wilson’s warbler is one of the less common transients which pass through southern New England on the way to their more northern breeding grounds. We find the birds most commonly, perhaps, in swampy thickets or roadside shrubbery, although often they frequent well-grown woodlands. They are also at times fairly common visitors to our city parks: the Public Garden in Boston, for example: during the height of the spring migration, at which time they seem to be in full song.
In the open country the birds as a rule appear singly, but in the parks they may collect in considerable numbers; Horace W. Wright (1909) reports 10 birds in the Public Garden on a single day.
Whenever we meet the little bird our attention is sure to be drawn to it by its bright song, and then the eye is caught by the quick sprightliness of its demeanor, and a flash of sunny gold.
Nesting: When we meet Wilson’s warblers during the spring migration they may be on their way to the far north, for they breed to the limit of trees in northwestern and central Mackenzie as well as in the more southern Provinces of Canada and in northern Maine and New Hampshire.
In the southern part of its breeding range, where it has been studied carefully, it chooses for nesting the moist sphagnum bogs which are characteristic of this region: lonely, mosquito-infested wastes where, often associated with yellow palm and Tennessee warblers, it builds its nest on the ground.
Philipp and Bowdish (1917) thus describe a typical nest found in New Brunswick. “On June 16, a nest with five eggs, in which incubation was well commenced, was found in a boggy and quite wet clearing, surrounded by woods, with a considerable growth of small cedar, tamarack, spruce, and balsam saplings. This nest was built in the side of a moss tussock, resting in the angle formed by the abrupt side of the tussock and a little cedar, at the base of which the nest was placed. It was composed of moss, dead leaves, fine weed stalks and grasses, a little hair being mingled with the lining of fine, dead grass. It measured 3.50 x 1.50 inches in depth and 3.50 x 1.75 inches in diameter.” Of the several nests found they say: “The nests are typical and readily distinguishable from other ground nesting warblers of the region, being very bulky for such a small bird.”
W. J. Brown (MS.) sends this interesting account of the habitat of Wilson’s warbler and the b~havior of the birds at the nest, drawn from his long “friendship” with the bird, and his intimate knowledge of some 75 of their nests. “In the County of Matane, Gulf of St. Lawrence there is a sphagnum bog three miles in circumference and over a mile across. It is hidden on the west, east, and south by heavy evergreen woods, while the north end extends to the seacoast. Throughout this bog the ground is covered with deep moss, while black spruce, tamarack, and pine saplings are scattered over the whole legion. The undergrowth is mostly Laborador tea and blueberry plants. Along the sides of this delightful barren are extensive open runs of alder, birch, and other mixed small timber, with many beautiful mounds interspersed. This region is the home of Wilson’s warbler, and the bird is not only abundant in this bog, but throughout the entire County of Matane. I use the word ‘friendship’ advisedly in the case of the Wilson’s because it is a confiding little bird, entirely lacking in fear during the nesting season. Should a warbler be flushed from a nest and you are in doubt as to its identity, wait a few seconds, and if it be a Wilson’s, the bird will immediately return and exhibit a mild curiosity and a look of inquiry, flitting about noiselessly, and probably will enter the nest while the intruder is standing near by. I have never seen this warbler fail to return at once to its nest after being flushed. This action is characteristic and quite contrary to that of Nashville and Tennessee warbiers.
“At the end of June, 1930, I flushed a Wilson’s warbler from a nest in a hummock well-sheltered by a thick bunch of Labrador tea, and near a fringe of alders. The nest contained five young a few days old. I sat down 3 feet from the nest for 2 hours, with an old hat on my head. The bird, returning with insects, perched on my hat, then on my shoulder, and into the nest. This happened 20 times while I was anchored at the nest The bird was fearless and tame and no doubt took it for granted that I was going to be a part of the landscape. Each time, on leaving the nest, she flew directly away. I did not see the male bird, but I heard him singing as he patrolled along the fringe of alders. I have found a nest of Wilson’s warbiers in this same mound every season for the past 10 years and I believe they become attached to old haunts. While I have been shuffling about with my camera and tripod, the birds are either perched on the camera and its base or are in the nest, sitting. This applies to most of the nests which I have observed.
“The majority of nests are sunk in moss at the base of alders or tamarack saplings at the edge of second growth. They are well hidden, and the bird sits close until almost trodden upon. They are sociable little birds with their own kind; three or four pairs may nest near together in a line of alders not over 75 yards long. The nests are simple affairs composed inside and out of a compact mass of fine, bleached grasses. After the young are hatched the male is often seen at the nest; before this time he patrols the alders, feeding and singing in a lazy way, with an occasional long flight to feed the sitting bird.”
Of the occurrence of Wilson’s warbler as a breeding bird in Maine, Knight (1908) says:
That the species breeds frequently in the Canadian life areas of northern and central Maine seems well established, and that it has not been more often discovered during the nesting season Is on account of the favorite habitats being rarely visited by ornithologists. Full sets of eggs may be sought between June first and June nineteenth. There seems to be no doubt at all that a person acquainted with the habits of the present species and the Yellow Palm Warbler as well, can go into territory in northern and central Maine and find both species in many localities where other observers have failed to see them, provided that suitable tracts of spruce and hackmatack bog exist In the region.
Horace W. Wright (1911) speaks of the bird as “a rare summer resident, but becoming less rare” in Jefferson, N. H. He found the birds settled in Jefferson in the summer of 1905, and during the following 5 years, a little colony of six males was established, lie reports also a nest and eggs found in 1909 by F. B. Spaulding in the neighboring town of Lancaster.
Eggs: Wilson’s warbler lays from 4 to 6 eggs to a set, most commonly five. These are ovate, with some tending toward short ovate, and they have only a slight lustre. They are white, or creamy white, finely speckled or spotted with “chestnut,” “auburn,” or “r~set,” with underlying markings of “light brownish drab” or “pale brownish drab.” Sometimes the markings are scattered well over the egg, but there is a tendency to concentrate at the large end, often forming a distinct wreath of fine specklings. On the more boldly marked eggs the drab tones are quite prominent, whereas on the finely marked eggs they are often absent. The measurements of 44 eggs average 15.9 by 12.4 millimeters; the eggs showing the four extremes measure 17.3 by 12.7, 16.8 by 13.2, and 14.0 by 11.4 millimeters (Harris).
Young: Two nests under the observation of W. J. Brown (MS.) at Matane County, Quebec, contained five fresh eggs on June 18, 1939. “The young appeared in both nests in the early morning of June 29. On July 10 both nests were empty. On the basis of these records, the incubation period lasts 10 to 11 days, and the young remain in the nest for the same length of time.”
Plumages: Dr. Dwight (1900) describes the juvenal plumage, in which the sexes are alike, as follows: “Above, sepia or hair brown, mottled with sepia. Wings and tail dull olive-brown, edged with olive-green; wing coverts paler and indistinctly edged with buff. Below, primrose-yellow washed with pale wood-brown on the throat and sides.”
The first winter plumage is acquired in July and involves a molt of all the body plumage and the wing coverts, but not the rest of the wings or the tail. The black cap is acquired, veiled with brownish feather tips; the upper parts become bright olive-green; the forehead, sides of the head, and the under parts become lemon-yellow.
The first nuptial plumage is acquired by a partial prenuptial molt, chiefly about the head and throat, young and old birds becoming indistinguishable.
A complete postnuptial molt occurs in July, at which an adult winter plumage is assumed that differs only slightly from the first winter plumage.
These remarks refer to the male. The plumages and molts of the female are similar, but the black cap is wholly lacking in the first winter plumage and more restricted afterward.
Food: No comprehensive study of the food of Wilson’s warbler has appeared in the literature, and practically nothing has been published in detail on the food of our eastern bird. Prof. Beal (1907) examined the contents of 53 stomachs of one of the western races of the species and found that 93 percent of the food was animal matter and only ‘1 percent of it vegetable. There is no reason to suppose that the eastern race has not a somewhat similar diet. Moreover, since our Wilson’s warbler has been seen repeatedly foraging among the twigs and foliage of trees and shrubs, presumably in search of insects and their eggs and larvae, or darting out into the air to capture flying insects, it may be safely regarded as primarily insectivorous and hence mainly a beneficent species.
Dr. Alexander F. Skutch (MS.), speaking of the bird in Central America, says: “Among the peculiar foods of the Wilson’s warblers in their winter home are the little, white, beadlike protein corpuscles which they daintly pluck from the furry cushions at the bases of the long petioles of the Cecropia tree. These minute grains, the chief nourishment of the Azteca ants that dwell in myriads in the hollow stems of the tree, are also sought by a number of other small birds, both resident and migratory.”
Mrs. Edith K. Frey tells me that she has seen Wilson’s warblers and several other species of wood warblers feeding on aphids in her shrubbery day after day until the pests were gone.
Behavior: Wilson’s warbler is a bright spot to bird watchers at the full tide of migration in May, and again in late summer, although we meet the bird less frequently during its southerly retreat from its breeding ground. It is a bright spot not solely because of brilliancy of plumage, but rather because it appears as a lively personality, standing out sharply as an individual among the quieter warblers. It gives us the impression of extreme alertness as it flits about in the trees and shrubbery, fluttering among the foliage, dashing into the air to capture flying insects, restless, full of energy, symbolizing, in spring, its characteristics by its brisk, vivid song. William Brewster (1930) thus pictures the bird:
Wilson’s Blackcap is a most interesting little bird, very like the Canadian Warbler in general behavior, but fussier and more animated. It feeds chiefly among low bushes (especially willows) near water and is incessantly in motion.
It is much given to making short, abrupt upward flights to seize insects from the under sides of the leaves. It jerks its tail upward every few seconds and also waves It from side to side much after the manner of a Gnatcatcher. It frequently darts out after flying insects and not infrequently descends to the ground to search for food among the fallen leaves. When on the ground It hops about briskly and often flutters its wings.
J. Merton Swain (1904) says of the bird on its breeding ground: “They feed in briery thickets, picking up insects very nimbly. They have the talents of a Flycatcher, and capture much of their food on the wing, but do not, like the Flycatcher, return to the same perch.”
Voice: Like most wood warbler’s songs, which in the main are little more than a series of squeaky notes, or at most shrill whistles, the song of Wilson’s warbler is neither beautiful nor artistic. Yet it stands out by reason of its brightness; the notes are delivered so emphatically, are so sharply cut and staccato, and follow each other in chattering haste so rapidly that the song has a distin~tive quality and is easily distinguished from those of those other warblers which sing on about the same pitch. At times the song may suggest that of the yellow warbler, but the latter, in comparison, has almost a drawling delivery; at other times it may suggest that of the Nashville, but here again the staccato quality marks it; it sometimes recalls for a moment the song of the northern waterthrush, but as all the notes are very short and never isolated, the resemblance at once vanishes; occasionally there is a hint of the goldfinch’s voice (I find this point mentioned more than once in my notes of the last quarter of a century), but the tone is too fiat for a goldfinch: it lacks the sweet, musical ring.
The song is more or less varied, but there are not two distinct songs as in the case of some warblers. In a common form the pitch drops in the second half when, the notes becoming faster and more emphatic, the song changes into a sort of chatter. I have heard this form given over and over for half an hour or more with little or no change. More rarely the pitch at the end may return to the original pitch, thus dividing the song into three parts. Occasionally the song ends with a single, emphasized note, and frequently neither pitch nor tempo varies: a perplexing song at first, but the extreme liveliness of the notes soon identifies the author.
Gerald Thayer (Eaton, 1914) gives this accurate description: “Its song suggests somewhat in miniature that of the Northern water thrush although it is its elf quite loud and rich, a bright, hurried, rolling twitter, suddenly changed into more of a trill, richer and somewhat lower in tone. The first portion of the song varies in length and richness, sometimes longer and fuller in tone, more often shorter and weaker than the second, while some individuals omit it altogether, uttering only the trill when the song is rather difficult to recognize. * * * The call note is a weak but ringing t3oAip.”
Aretas A. Saunders (MS.) sends the following: “The song of Wilson’s warbler is mainly a series of rapid chatterlike notes, dropping downward in pitch toward the end. It is not especially musical in quality. The notes are short, staccato, and with marked explosive consonant sounds. I have had opportunity to record only songs heard on migration, and since the song is not often heard then, I have only 12 records. These have from 8 to 15 notes, averaging about 10. They vary from F”‘ to C”” in pitch, and from 12/s to 14,~ seconds in length. Individual songs have a pitch range from one to two and a half tones, averaging about one and a half. In most of the records the notes are all on the same pitch and of equal length at the beginning, only the last 3 or 4 notes dropping in pitch, and sometimes becoming faster in time. In all but 2 records the last note is lowest in pitch, and in these exceptions it is the next to the last note that is lowest. A typical song would sound like witititititititatoo.” Ralph Hoffmann (1899) reports: “On the 2d of November I found a female Wilson’s Blackcap in Belmont [Mass.]; the bird stayed in the same locality till Nov. 20, and uttered when startled a curious wren-like leele,kek, which I have never before heard.” Field mark8: Although the identification points in the plumage of Wilson’s warbler are mostly negative: absence of wing bars and tail spots, and no streaks or lines in the plumage: the tiny bird is distinctive in the field. The black skull cap is often difficult to see, but the contrast between the plain darkish back and the brilliant, plain under parts is an aid in identification, and even more helpful is the unmarked, bright yellow side of the head with the black eye, a dot rn the center. Enemies: Wilson’s warbler presumably has few enemies aside from danger during its long migration and the hazards of a ground nest. Wilson’s warbler, like the Tennessee and yellow palm, is apparently rarely molested by the cowbird. The three species breed in the same environment, often in the same swamps, where, it may be supposed, cowbirds seldom go. Friedmann (1929) does not list the bird, but records the race chry8eola as “a not uncommon victim of the Dwarf Cowbird in southern California.” Fall: Of the bird in Cambridge, Mass., in the fall, William Brewster (1906) says: “During their return migrations, which begin late in August, Wilson’s Blackcaps are decidedly less numerous: or at least conspicuous: than in spring, and also more given to haunting dry places. Indeed I have seen them oftenest at this season among oaks or pines growing on high ground. Most of them pass southward before the middle of September, but Mr. Ralph Iloffmann has reported finding a young bird in Belmont as late as November 20 (1898) .”
Winter: Dr. Alexander F. Skutch (MS.) sends to A. C. Bent the following comprehensive account of the bird as he has seen it during the winter in Central America: “All three forms of Wilson’s warbler pass the winter months in Central America. Of these, the race that breeds in the Rocky Mountains, the pileolated warbler, appears from the determination of specimens to be far the most numerous. Yet since all three may occur in the same locality and it is difficult or impossible to distinguish them in the field, it seems best to treat them all under the name of the typical form.
“Arriving early in September in Guatemala, and about the middle of the month in Costa Rica, Wilson’s warblers rapidly increase in numbers until they are among the most abundant of wintering warbiers. They settle down for their long sojourn in a great variety of situations, from the warm lowlands up to the bushy summits of the higher mountains that are so cold and frosty during the nights of the northern winter. I have found them abundant even at 11,000 feet above sea level. They are far less common in the Caribbean lowlands, than they become above 1,500 feet, and are distinctly uncommon on the Pacific side of Central America below 2,000 feet. But from these levels up to the tree line, there seems to be slight variation in their midwinter abundance, which is associated with the type of vegetation rather than with altitude. Everywhere the blackcaps haunt the bushy abandoned fields, neglected pastures, openings in the forest, hedgerows, and at times even the dooryard shrubbery. They avoid the sunless undergrowth of heavy forests, yet frequent the lighter woods of oak and pine in the highlands, and the thinner of the woodlands at lower elevations. Restless and sprightly, they flit tirelessly among the bushes in pursuit of tiny insects, constantly advertising their presence with their emphatic nasal chip.
“The period of absence of Wilson’s warbler from Central America is brief. On the Sierra de Tecp~n in the Guatemalan highlands, I saw the last one of the season on May 22, 1933. The first fall arrival was encountered on September 3 of the same year; four were seen on the following day, and by the fifth of the month, they were so numerous that it was hopeless to try to keep count of them. They had been absent only 3 months and 12 days. At Vara Blanca on the Cordillera Central of Costa Rica, the first appeared on September 18, 1937, and the last was seen on May 5 of the following year. They were present through the year, save for a period of 4 months and 13 days.
“Although at times Wilson’s warblers are present on the bushy mountain slopes in such great numbers that they give the impression of being gregarious, they are in fact evenly distributed through the bushes. Where less abundant, they are seen singly rather than in flocks, for they are intolerant of the company of their own kind during the winter months. At times, in the highlands, a single individual of the species will attach itself to a mixed flock of warbiers and other small birds. On the central plateau of Costa Rica, I would sometimes find a single Wilson’s warbler keeping company among the coffee bushes with a pair of the pretty, chestnut-headed Delattre’s warblers (Basilenterus delattrii), a resident species which remains paired and maintains a territory throughout the year. But perhaps more often the blackcaps pass the winter quite alone. On October 12, 1933, I came upon: two male ‘Wilson’s warblers fighting earnestly on the ground in the garden of the house in which I dwelt on the Sierra de Tecp~n. ‘While I did not witness the beginning of the conflict and can only surmise its cause, it seems probable that this was a struggle for the p6ssession of the garden in which it was staged. They separated a few moments after I came upon them; and I did not hear them sing, as migratory warblers will sometimes do under similar circumstances. As the date for their departure approach’es, these long-solitary warblers tend to draw together in flocks for their northward flight.
“On April 27, 1933, I heard a ‘Wilson’s warbler singing in the Guatemalan highlands. Five days later, I found another caroling far more whole-heartedly, repeating several times over his simple but happy little lay, a rapid chipping gradually ascending in pitch. These songs hearalded their northward departure. By the latter part of April, few Wilson’s warblers remain in Costa Rica, although they have been recorded as late as May 5. In Guatemala they linger somewhat later, a few individuals tarrying until past the middle of May. Long before they depart from Central America as a whole, these warblers appear to withdraw from the lower altitudes at whi~h they are not uncommon earlier in the year, probably merely ascending the mountains to higher levels. Thus, in the lower Motagua Valley in Guatemala, at about 500 feet above sea level, I found them fairly abundant in January and February, but did not record them later. In the Pejivalle Valley of Costa Rica at 2,000 feet, I found a number in February, 1934, but failed to see aï single one when I revisited the locality in April, 1941. In the Basin of El General, on the Pacific side of the same country, they may be exceedingly numerous at an altitude of 3,000 feet from their fall arrival until the following March, when they rapidly grow more silent and become fewer. In dry years they are seen in April only as rare transients,, while in abnormally wet years they may remain somewhat more numerous. This local movement, well in advance of the main northward migration, is paralleled by that of the Tennessee warbler; it appears to be caused by increasing dryness or higher temperatures, or by the two in combination.
“Early dates of fall arrival in Central America are: Guatemala: passim (Griscom), September 11; Sierra de Tecp~in, 8,500 feet, September 3, 1933; San Juan Atit~n, September 8, 1934; Huehuetenango, September 11, 1934. Costa Rica: La Hondura (Carriker), September 22; Vara Blanca, September 18, 1937; San Miguel de Desamparados, September 20, 1935; El General, September 18, 1936.
“Late dates of spring departure from Central America are: Costa Rica: El General, April 22, 1936 and April 24, 1937; Vara Blanca, May 5, 1938; Juan Vifias (Carriker), April 19. Guatemala: passim (Griscom), April 26; Sierra de Tecp~n, May 22, 1933.”
Range: North America and Central America.
Breeding range: The pileolated warbler breeds north to northern Alaska (Kotzebue Sound, probably Barrow, and Fort Yukon) ; northern Yukon (La Pierre House); northwestern and central eastern Mackenzie (Fort MacPherson, Mackenzie Delta, and Fort Anderson); northeastern Manitoba (probably York Factory); northern Ontario (probably Moose Factory) ; central Quebec (Mistassini Post, Mingan Islands, and Mutton Bay); southern Labrador (probably Hamilton River, Cartwright, and Squasho Run); and Newfoundland (Saint Anthony, Lewisport, and Trinity). East to Newfoundland (Trinity); central Nova Scotia (Kings County and Halifax); and Maine (Macbias). South to Maine (Macbias, Augusta, and Fryeburg); northern New Hampshire (Lancaster and Jefferson); northeastern Vermont (Saint Johnsbury); southern Quebec (Sherbrooke); southern Ontario (Sudbury, Madoc, and Ottawa); northern Michigan (Baraga and Blaney Park); northern Minnesota (Mud Lake and Duluth); western Texas (probably Guadalupe, Davis, and Chisos Mountains); north-central New Mexico (Santa Fe Canyon); and southern California (Julian and Escondido). West to California (Escondido, Riverside, Mount Whitney, Eagle Lake, and Edgewood); western Oregon (Mount Hood and Fort Klamath) ; western Washington (Bellingham, Seattle, and Mount Rainier); British Columbia (Victoria); and Alaska (King Cove, Kodiak Island, Cordova Bay, Chitina Moraine, Sitka, Gravina Island, Norton Sound, and Kotzebue Sound).
Winter range: This species winters north to southern Baja California (La Paz) ; southern Sonora (Tesia, and Alamos) ; Nuevo Le6n (Monterrey, and Linares) and southernmost Texas (Santa Maria). East to southernmost Texas (Santa Maria) ; Tamaulipas (Victoria); Costa Rica (Guayabo, San Jos6, and Cerro de Santa Maria); and Panama (Veraguas). South to Panam~i (Veraguas, Chiriqui, and Boquete); and Guerrero (Chilpancingo). ~Vest to Guerrero (Chilpancingo) and southern Baja California (San Jos6 del Cabo and La Paz).
The range as outlined is for the entire species of which three subspecies are recognized. The Wilson’s pileolated warbler (Wilson~ p’usilla pusilia) breeds from northwestern and central Mackenzie to Nova Scotia and New England, northern Michigan, northern Minnesota, southern Manitoba, central Saskatchewan and central eastern Alberta; the northern pileolated warbler (lv. p. pileolata) breeds in northern Alaska, northern Yukon and northwestern Mackenzie, Montana, eastern Wyoming, southwestern Colorado, north-central New Mexico, and western Texas, and south from Alaska through the Rockies and mountains of the Great Basin to northeastern and central eastern California; and the golden pileolated warbler (W. p. chr yecola) breeds along the coasts and coastal ranges from southwestern British Columbia, south through western Washington, western Oregon, to eastern and southern California.
Casual in Florida (Tallahassee, Sharpes, and Fort Myers); Missouri (Independence); and Mississippi (Gulfport).
Migration: Late dates of spring departure are: Costa Rica: Basin of El General, April 24. Guatemala: above Tecp~in, May 22. Baja California: Sierra San Pedro M~irtir, May 21; Sonora: iRancho La Arizona, western foothills of Pajaritos Mountains, May 25.
Early dates of spring arrival are: Alabama: Florence, May 1. Georgia: Milledgeville region, April 13. South Carolina: Chester, May 10. North Carolina: Salisbury, May 8. Virginia: Charlottesville, May 4. West Virginia: Bee, April 24; French Creek, May 7 (average of 10 years, May 12). District of Columbia: Washington, May 1 (average of 38 years, May 8). Maryland: Baltimore County, May 4. Pennsylvania: Renovo, May 1. New Jersey: Long Valley, May 5; Union County, May 12 (average, May 15). New York: New York City, April 30. Connecticut: Hartford, May 3. Rhode Island: Kingston, May 8. Massachusetts: Huntington, May 1. Vermont: Wells River, May 6. New Hampshire: Monroe, May 5. Maine: Lewiston and Winthrop, May 7. Quebec: Montreal, May 13. New Brunswick: Saint John, May 15. Nova Scotia: Halifax, May 18. Newfoundland: St. Andrews, May 27. Labrador: Grand Falls, Hamilton River, May 31. Louisiana: Monroe, April 16. Arkansas: Rogers, April 27. Tennessee: Elizabethton, May 4. Kentucky: Bowling Green, April 18. Missouri: St. Lou is, and St. Charles, April 29. Illinois: LeRoy, April 27; Chicago, May 6 (average, May 11). Indiana: Marion County, April 28. Ohio: South Webster, April 25; central Ohio, May 2 (average, May 11). Michigan: Ann Arbor, May 11. Ontario: Toronto, May 10; Ottawa, May 14 (average of 17 years, May 20). Iowa: Buchanan County, May 7. Wisconsin: Madison, May 4. Minnesota: Lanesboro and Minneapolis, May 2 (average of 39 years for southern Minnesota, May 10). Texas: Brewster County and Victoria, April 1; El Paso, April 6. Oklahoma: Gate, April 22. Kansas: Douglas County and Lake Quivira, Johnson County, May 2. Nebraska: Hastings, April 26. South Dakota: Sioux Falls, May 3. North Dakota: Fargo, May 8; Cass County, May 11 (average May 17). Manitoba: Aweme, May 3 (average, May 18). Saskatchewan: Indian Head, May 14. Mackenzie: Mackenzie Delta, May 28. New Mexico: Glenrio, April 15. Arizona: Tucson, March 7; Holbrook, May 4. Colorado: Monon, Baca County, May 3. Utah: Uinta Basin, May 12. Wyoming: Laramie, May 2. Idaho: Moscow, May 11. Montana: Anaconda and Fortine, May 14. Alberta: Medicine Hat, May 17. California: El Caj on, March 8; San Francisco Bay area, March 12 (average of 22 years, March 24). Nevada: Charleston Mountains, April 30. Oregon: Newport, April 13. Washington: Lapush, April 10. British Columbia: Comox, Vancouver Island, April 14. Yukon: Carcross and Ross Post, May 22. Alaska: Kake, May 5; Nushagak, May 10; Kotzebue Sound region, June 3.
Late dates of fall departure are: Alaska: Nome, August 27; Nuniyak Island, September 7. Yukon: Macmillan River region, September 16. British Columbia: Okanagan Landing, September 22. Washington: Seattle, September 25; Pullman, September 18. Oregon: Eugene area, September 24; Government Island, December 11. Nevada: Montello, and West Humboldt Mountains, Pershing County, September 20. California: Hastings Reservation, Monterey County, November 1; Eureka, November 20. Alberta: Warner, September 30. Montana: Sun River, October 7. Idaho: Moscow area, October 21. Wyoming: Parco, October 18; Laramie, October 16, November 10 and 11. Utah: North Creek, Beaver, September 26. Colorado: Pueblo, October 20. Arizona: Tucson, October 28; average of 5 years for Parker, Topock area, September 30. New Mexico: Apache, October 15. Mackenzie: Artillery Lake, September 5. Saskatchewan: East End, September 29. Manitoba: Aweme, September 21. North Dakota: Fargo, October 20; Cass County, September 19 (average, September 15). South Dakota: Faulkton, October 10 and 30. Nebraska: Red Cloud, September 28. Kansas: Gore County, October 9. Oklahoma: Cimarron County, September 23. Texas: Victoria, November 14; Cove, November 16, January 1. Minnesota: Montevideo, October 5; Minneapolis, October 20 (average of 10 years for southern Minnesota, September 21). Wisconsin: Racine, October 8. lowa: Tabor, October 3. Ontario: Ottawa, September 25 (average, September 19). Michigan: Grand Beach, October 18; Hillsdale, December 8. Ohio: central Ohio, September 30 (average, September 24). Indiana: Monroe County, October 3. Illinois: Chicago, October 5 (average, September 19); Port Byron, October 11. Missouri: Columbia, September 30. Kentucky: Bowling Green, October 1. Tennessee: Nashville, October 10. Arkansas: Rogers, October 7. Mississippi: Saucier, October 12. Louisiana: Cameron, November 21; Baton Rouge, October 24, December 20. Newfoundland: Tompkins, September 30. Quebec: Quebec, September 15. Maine: Jefferson, October 11. New Hampshire: Warren, October 3. Vermont: Clarendon, September 29. Massachusetts: Belmont, November 20; Groton, November 27; ïXVest Gloucester, November 29; Boston, December 3. Connecticut: Hartford, October 1; Windsor Hill, November 3. New York: New York City, October 31, November 22 and 25; Orient Point, Long Island, November 24. New Jersey: Sandy Hook, October 7; Union County, September 29 (average, September 25) Princeton, December 23. Pennsylvania: Laceyville, October 15; Radnor, December 7. Maryland: Baltimore County, and Patuxent Wildlife Research Refuge, Laurel, September 23; Snow Hill, December 22. District of Columbia: Washington, October 13 (average of 8 years, September 19). West Virginia: French Creek, September 30. Virginia: Charlottesville, October 0. North Carolina: Piney Creek, October 11. South Carolina: Mount Pleasant, November 9. Georgia: Fitzgerald, October 31. Alabama: Birmingham, October 6. Florida: Pensacola, November 11; Lake Jackson, December 19; Tallahassee, January 1. Sonora: San Jos6 Mountains, October 25.
Early dates of fall arrival are: Washington: Seattle area, August 14. Nevada: Charleston Mountains, August 13. California: Santa Cruz Island, August 29. Montana: Great Falls, August 17. Idaho: Moscow area, August 10. Arizona: Tucson, July 31. New Mexico: Willis, August 8; Cooney, August 20. North Dakota: Wilton, August 15; Cass County, August 16 (average, August 21). Nebraska: Gresham, August 20. Kansas: Douglas County, and Geary, Doniphan County, August 23. Oklahoma: Cimarron County, August 25. Texas: Austin region, August 6; El Paso region, August 27. Minnesota: Hibbing, August 13; Minneapolis, August 15 (average of 9 years for southern Minnesota, August 24). Wisconsin: Mazomanie, August 26. Iowa: Winnebago, Au gust 17. Michigan: Sault Ste. Marie, August 24. Ohio: central Ohio, August 20 (average, August 27). Indiana: Lake County, August 28. Illinois: Chicago, August 17 (average, August 24). Missouri: La Grange, August 16. Kentucky: Versaille and Bowling Green, September 6. Tennessee-Knoxville area, August 12. Arkansas: Winslow, September 7. Mississippi: Bolivar County, September 10. Louisiana: Baton Rouge, September 11. Maine-Hog Island, August 6. New Hampshire: Hancock and Monroe, August 16. Vermont: Wells River, August 20. Massachusetts: Lynnfield, August 19. Connecticut: New Haven and West Hartford, August 27. New York: New York City, July 26; Bayside, Long Island, July 31. New Jersey: Englewood region, August 15; Union County, August 20 (average, September 1). Pennsylvania: Crawford County and Pittsburgh, August 28. Maryland: Patuxent Wildlife Research Refugee, Laurel, August 17. District of Columbia: Washington, August 22. Viigirna: Shenandoah National Park, August 19. North Carolina: Piney Creek, September 4. Georgia: Athens, September 2. Alabama: Birmingham, August 23. Florida: Pensacola, September 23. Cuba: western Cuba, September 24. Mexico: Sonora, Rancho La Arizona, western foothills of Pajaritos Mountains, August 16; Baja California: San Jos6 del Cabo, August 25. Guatemala: above Tecpiin, September 3. Salvador: Monte Mayor, Volc~n do Sociedad, October 6. Costa Rica: Basin of El Genera], September18.
Egg dates: Alaska: 10 records, May 20 to July 3; 5 records, June 15 to 18.
California: 82 records, April 27 to July 4; 41 records, May 10 to June 10, indicating the height of the season.
Colorado: 17 records, June 2 to July 1; 9 records, June 12 to 20. Maine: 2 records, June 4 and 22.
New Brunswick: 7 records, June 6 to 21 (Harris).
NORTHERN PILEOLATED WARBLER
WILSONIA PUSILLA PILEOLATA (Pallas)
The western representatives of Wilsonia pusilla are divided into two subspecies, the northern pileolated warbler (W. p. pileolala) and the golden pileolated warbler (W. p. cliryseola). The former breeds from the northern tree limit in Alaska, southward along the coast to the Queen Charlotte Islands, and farther southward, mainly in mountain regions, as least as far as New Mexico and perhaps centralwestern Texas. Dr. E. W. Nelson (1887) calls it “one of the commonest of the brush-frequenting species in the north and extends its breeding range to the shores of the Arctic Ocean, where it is found breeding about Kotzebue Sound as well as along the eastern coast of Norton Sound wherever shelter is afforded.” Dr. herbert Brandt (1943) says: “In the Ilooper Bay area the Pileolated Warbler confines itself to the brushy flanks of the Askinuk Mountains where it is a rather common breeder. Along the lower Yukon River, however, during early July I recorded it at every landing that we made as far up as Mountain Village.”
Referring to its status in Montana, Aretas A. Saunders (1921) writes: “A common summer resident of the mountains in the western half of the state, and a common migrant in the mountain valleys and at the edge of the prairie region near the mountains. A rare migrant in the eastern part of the state. Breeds in the Canadian zone, in willow thickets along the mountain streams or bordering mountain lakes. West of the divide the Pileolated Warbler breeds in arborvitae forests.”
It probably breeds in eastern Oregon, but Gabrielson and Jewett (1940) say that “the first actual Oregon nest remains to be discovered.” According to Prof. Cooke (1904), “in Colorado it breeds commonly at timberline, ranging from 12,000 down to 6,000 feet.” The northern pileolated warbler is much like the eastern Wilson’s warbler, but it is somewhat larger on the average and its coloration is brighter, the upper parts being more yellowish olive-green and the yellow of the under parts brighter. It is, however, not so brightly colored as the golden pileolated warbler that breeds in California.
Spring: From its winter home in Mexico and Central America this subspecies makes a long flight to northern Alaska, and over a wide range, from the Pacific coast to the eastern foothills of the Rocky Mountains. It is a later migrant in California than the local breeding form. Mrs. Amelia S. Allen tells me that the golden pileolated warblers generally arrive on their breeding grounds in March or very early in April, sometimes as early as March 11. She says in her notes: “About the middle of May, after the breeding birds are busy nesting, migrating birds pass through on the way north.”
Harold S. Gilbert writes to me: “On June 11, 1933, Mr. Everett Darr, of the Mazamas, found 200 frozen pileolated warblers scattered over tbe snow and ice at about 10,000 feet elevation, in the crater of Mt. St. Helens, Wash. He brought some of these birds to my office for identification. Apparently, during migration they had been swept up in a storm and frozen.”
Nesting: Herbert Brandt (1943) found five nests of this warbler in Alaska, of which he says:
The nest of the Pileolated Warbler in the Hooper Bay area Is found only in the vicinity of the willow and alder thickets that decorate the lower mountain slopes. Out In the cleared defiles and under the matted dead grass that never again rises from its supine position after being beaten down by winter’s pressure, this little bird builds its home. The nest may be sunken flush with the mossy sod, or it may be built In the center of a large grass tuft, in which case it may be elevated a few incifes above the surrounding floor. However, so closely hidden is it that considerable search is required to discover the dainty abode.
The nest is made entirely of short grass straws thnt are not interwoven, and the structure is therefore so fragile that it will scarcely retain Its form when removed. The lining may be entirely of fine, thread-like grass shreds, or there may be admixed therewith considerable coarse dog hair. If the latter is used, each hair is laid in separately, and none of the wool-like tufts of the dog’s undercoat is employed. The measurements of five nests are: height, 2.00 to 3.50; outside diameter, 3.00 to 4.00; inside diameter, 1.75 to 2.00; and inside depth, 1.50 to 1.75 inches.
H. D. Minot (1880) thus describes a Colorado nest: “The nest was sunken in the ground, on the eastern slope or border of the swamp, at the end of a partly natural archway of long dry grass, opening to the southward, beneath the low, spreading branch of a willow. It is composed of loose shreds, with a neat lining of fine stalks and a few hairs, and with a hollow two inches wide and scarcely half as deep.”
Dr. Joseph Grinnell (1909) writes: “A nest of the Alaska pileolated warbler was found by Stephens on the 7th of June near Hasselborg Lake, Admiralty Island. It was in the thick moss growing among the roots of an uprooted tree in a creek bottom. The nest was about five feet from the ground and occupied a niche in the mass of moss which overhung and hid it. The nest consists externally of moss, weathered leaves, and bark strips; internally of deer hair.”
Eggs: All of the 5 nests found by Brandt in Alaska contained 6 eggs each, but farther south the numbers run from 3 to 5, four being the commonest number. The eggs are apparently indistinguishable from those of Wilson’s warbler. Dr. Brandt (1943) describes his eggs as follows: “The spots are irregular in shape, angular, and range in size from the finest pepperings to small dots. These are often confluent at the larger end, forming a broad zone or wreath. A few weak markings are scattered towards the small end which is almost unmarked. The markings are of two types: the richer one which is more frequent is of red colors, ranging from brick red to Indian red, with the weaker underlying markings vinaceous lavender. The latter are inconspicuous and often just peer out from beneath the bolder overlying spots.” The measurements of 40 eggs average 15.8 by 12.2 millimeters; the eggs showing the extremes measure 17.2 by 12.6, 16.0 by 13.1, 14.7 by 12.2, and 15.2 by 10.7 millimeters.
Plumages: The molts and plumages of the two western races correspond to those of the eastern race and their food is probably similar; in fact, the three do not differ materially in any of their habits, except as these are affected by their environment.
Behavior: Mrs. Bailey (1902) writes attractively:
Seen in migration when the dainty pileolated warbler has plenty of leisure, his airy ways are peculiarly charming. He usually hunts in low hushes, and as he suddenly appears through a chink in the dull chaparral wall the intense briulant yellow of the little beauty set off by his shining Jet black crowa gives you a thrill of surprise and delight.
He is winningly trustful and will come close to you and with wings hanging turn his head and look up to you from under his jaunty cap, then whip along with a jerk of his taiL As he goes he stops to run up a twig, leans down to peck under a leaf, flutters under a spray like a hummingbird, and then flies off singing his happy song.
Fall: This warbler seems to be more abundant, or more conspicuous, on the fall migration east of the Rocky Mountains, where it is often the commonest of all the wood warblers, even as far east as ivestern Nebraska.
Winter: Of its winter haunts in Mexico, Dr. Beebe (1905) writes:
The Pileolated Warbler and the Western Onateatcher were two small friends which we first met at the edge of the barranca. They were cheerful little bodies. forever busy searching leaves and twigs and flowers for tIny insects. Perhaps to this unflagging activity was due the fact that they seemed ahie to find a substantial living in all sorts and conditions of p]aces. The Pileolated Warbler: so like our Wilsoa Black-cap, but of brighter yellow: never became common, and yet in every list of birds we made, whether of upland, marsh, cactus desert, l,arranca, or tropical jungle, he was sure to have a place. He was not particular as to his winter home, but found everywhere enough to keep his blackcrowned little head busy picking and picking, interpolating a sharp chip! now end then, between mouthfuls.
In El Salvador, according to Die key and van Rossem (1938), “the northern pileolated warbler was found to be a rather common winter visitor between the elevations of 3,500 and 8,500 feet. * * * In its winter home this warbler is chiefly an inhabitant of low growth beneath the forest. Coffee groves are particularly favored in the lower elevations. On Los Esesmiles many were noted in the cloud forest, but there were even more in the arid associations such as oak scrub, bracken beneath the pines, and blackberry tangles along small %vatercourses.”
GOLDEN PILEOLATED WARBLER
WILSONIA PUSILLA CHRYSEOLA Ridgway
This brilliantly golden race of the pileolated warbler is confined in the breeding season to the Pacific coast district, from southern British Columbia to southern California, mainly west of the mountain ranges. Ridgway (1902) describes it as similar to Wilson’s warbler, “but slightly smaller and much more brightly colored; olive-green of upper parts much more yellowish, almost olive-yellow in extreme examples; yellow of forehead and superciliary region (especially the former) inclining more or less to orange; yellow of under parts purer, more intense.”
Samuel F. Rathbu~ tells me that in western Washington this is “probably the most common of all the warblers and occurs all through the region. from the foothills of the Cascades to the Pacific Ocean.”
In the Lassen IPeak region of California, according to Grinnell, Dixon, and Linsdale (1930),”this race of pileolated warbler in sum mer was limited closely to alder and willow thickets bordering ponds, along streams and in and around the edges of moist meadows. These two plants, alder and willow, appeared to furnish the chief factors favoring the initial choice of this habitat, rather than any of the plants associated with them.” Such haunts seem to be favored by the species in other parts of its western range.
Spring: Rathbun tells me that it arrives in western Washington about the first of May. “It differs in some ways from the rest of the warbiers: there is no straggling in their arrival; a goodly number come all at once, followed by the regular run of the birds until all have settled down. In the Olympic region, at least., they stick quite close to the tidewater. Sometimes one can stand on the beach facing the ocean and hear the warbler’s song directly behind in the woods; this is one of the very few birds of which this can be said.”
Nesting: Rathbun describes in his notes two nests found near Seattle. One was located about a foot above the ground “in a salal shrub that grew by the side of an old path through the rather dense forest, with a quite heavy undergrowth. The nest consisted, outwardly, entirely of dry, dead leaves, next to which were finer and softer ones of the same character and a little shredded inner bark of a cedar, the lining being fine rootlets and a few horsehairs.” The other was “built quite close to the ground on a slight elevation in a mass of dead bracken, being so well concealed that it was found only by flushing the female. It was composed outwardly of dead leaves and decayed weed stalks with a little green moss interwoven, this forming a base on which rested the main part of the nest, consisting of fine, dry weed stalks and shredded strips of the soft inner bark of a cedar, next being very soft, dry leaves, with a lining of fine, dry grasses. The whole structure was beautiful, the material being well interwoven and the construction neat. The outside height was 4 inches, outside diameter 6, inside diameter 2, and inside depth 1~4 inches. The location was well within a growth of young firs, widely scattered so that rather open spaces existed, overgrown with bracken.”
James B. Dixon tells me that he found the golden pileolated warbler nesting in Mono County, Calif., at elevations betwen 7,000 and 9,200 feet. And in the Yosemite region, Grinnell and Storer (1924) found a nest that “was in a depression in an earth bank at the base of two azalea stems. It was overhung by these stems and also by a mat of dead brakes, which concealed the eggs from view above. The foundation of the nest was of loosely laid dead leaves, and this graded into the rest of the structure, which was composed of leaves and grass blades. The fine lining was chiefly of deer hair. The structure measured about 31/2 inches in diameter outside, and the cavity was 2 inches across and 11/4 inches deep.”
J. Stuart Rowley writes to me: “The nests which I have found were all well-made, deep-cupped affairs and were all placed on the ground, either at the base of a clump of skunk cabbage or of a small sapling or shrub.”
Eggs: From 3 to 5 eggs, most often 4, make up the set for the golden pileolated warbler. These are, apparently, indistinguishable from those of other races of the species. The measurements of 40 eggs average 16.2 by 12.4 millimeters; the eggs showing the four extremes measure 17.0 by 18.0, and 15.0 by 11.9 millimeters.
Young: Mrs. Amelia S. Allen says in her notes: “I flushed a female from her nest about a foot from the ground in dense bracken. I sat down 6 feet from the nest and she returned almost immediately and regurgitated food, then brooded the three young that had been hatched recently. Then she spent 4 minutes hunting for food, returned, fed the young, and brooded 8 minutes.” A few days later torrential rains fell for 4 days, after which she found “a water-soaked nest containing five naked young that had been drowned.”
Mrs. Wheelock (1904) says:
The first brood is usually hatched early in May, and Is fed by regurgitation by both parents until four or five days old, when the usual food of small Insects and little green worms is given to them In the fresh state. As soon as their nursery days are over, the male takes entire charge of the nestlings, feeding them for ten days or two weeks longer.
For the second brood a locality slightly higher up the mountain may be chosen, but oftener the little mother builds her second nest within a hundred yards of the first, commencing it alone, while the male is still occupied with the first series. Incubation lasts twelve days, and is, I think, attended to solely by the female, although the male is frequently at the nest both to feed her and to watch over: but not brood: the eggs.
Food: Prof. Beal (1907) examined 52 stomachs of the golden pileolated warbler, and says:
Animal matter amounts to over 93 percent, vegetable to less than 7 percent. Of the former, the larger item Is Hemiptera, which aggregates over 35 percent. The black olive scale was found in four stomachs, but leaf-hoppers make up the bulk of this portion of the food. Hymenoptera stand next in importance, with 31 percent, made up of both wasps and ants. Flies are eaten to the extent of 11 percent, and in connection with the Hymenoptera proves what observations of Its habits Indicate, that this bird gets much of its food when on the wing. A good many of the insects were the tipulids, or crane-flies. Beetles of half a doxen different families were eaten to the extent of about 9 percent. They were mostly leaf-beetles (Chrysomelidne), with a few weevils and one or two others. No coccinellids were found. Somewhat less than 5 percent of the food consists of caterpillars. They do not appear to be favorite food, for they are eaten very~ Irregularly. Spiders also are taken only sparingly, and form but little more than 1 percent of the total food.
The vegetable food, less than 7 percent of the total, is made up almost entirely of fruit pulp, and was eaten in the months of September and October.
Behavior: Grinnell and Storer (1924) write:
Pileolated Warbiers do most of their foraging within 6 feet of the ground and practically never ascend far into trees even to sing. They keep within the cover of the lower stratum of foliage and are therefore only to be caught sight of momentarily. The birds are noted for their habit of darting out after flying insects; indeed one book name of the eastern relative of the pileolated is “black-capped fly-catching warbler.” Of all our other warhlers only the Tolmie is likely to be found in the same cover inhabited by the Pileolated Warbler. The Tolmie often forages out Into the drier chaparral, whereas the present species adheres closely to damp situations, either over boggy ground or else within a few yards of a stream. In favorable country, pairs of Pileolated Warbiers may occur as frequently as eight or even more to a linear mile.
Voice: On this subject Grinnell and Storer (1924) say:
The song of the Pileolated Warbler Is far less shrill than that of the Yellow Warbler and is less clear and more mechanical than that of several other warbiers. The syllables are given all on about the same pitch and about as rapidly as a person can pronounce them, but with the intervals shortening and the emphasis decreasing toward the end of the series; tshiip, tshap, tshup-t8huptshup-tshup. The call note Is not nearly so sharp as that of other warhiers, hut, on occasion, appeals to one as surprisingly loud for the size of the bird. It has an unmistakable quality of its own. Singing is done largely within the cover of the shrubbery; in other words this species does not, as do so many brush dwellers, seek out prominent song perches.
Mrs. Allen writes to me: “The song of this warbler is a series of rather sharp staccato notes without much change of pitch. It is not a trill, but rather a rapid series of chips. The call note is easily recognized because it is not a chip, but a thin wiry chee-ec, with some of the quality of the call note of the western winter wren.~~ Ralph Iloffmann (1927) says: “Beginners find it difficult to distinguish the song of the Pileolated from that of the Lutescent, with which it is often associated. The distinction lies in the sharpness and staccato quality of the Pileolated’s notes, and the final crescendo. There is of course much individual variation, but the typical song may be written: chit-chi, cliit-chi, chit-chi, chit-chi, chit-chi CHili’ CHIT CHIT; the song of the Lutescent is softer, more trilled and generally trails off at the close into weaker notes in a lower pitch. The call note of the Pileolated is diagnositic, a husky tsik or tachele, suggesting a Yellow-throat’s but not so heavy.”
Field marks: This species can be recognized by its black cap, very prominent in the male and usually more or less in evidence in the female; young females, in which the black cap is missing, and juvenals resemble female or young yellowtbroats, but the latter are more suffused with brownish, the olive and yellow colors in the former being clearer. It is the only western warbler that is wholly olive above and wholly yellow below, with a black cap and with no white rn wings or tail. The golden pileolated warbler can be easily distinguished from the northern by its much brighter colors. The song and the call notes are quite distinctive.
Enemies: According to Friedmann (1929) this warbler is “a not uncommon victim of the Dwarf Cowbird in southern California.”
Fall: Rathbun (MS.) writes from Seattle: “About the middle of August, the golden warbler will often be seen about the city, this being an indication of the fall migration; individuals continue to be noted until about the middle of September. At this time the only note given is a harsh squeak, and the males are very beautiful in their bright, fresh plumage. They will generally be found in the company of the California yellow warbler, one or two of the golden with a number of the yellow warbler.”
The fall migration through California, in company with other warblers and vireos, occurs mainly in September. Ralph Hoffmann (1927) says: “the Pileolated Warbler is one of the commonest birds in migration; at times every oak tree or tangle of low bushes seems alive with their bright and active forms.”